/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.jena.sparql.syntax;

import org.apache.jena.sparql.serializer.FormatterElement;
import org.apache.jena.sparql.util.NodeIsomorphismMap;

/** Element - abstract class for all pattern elements */
public abstract class Element
{
    public abstract void visit(ElementVisitor v);

    @Override
    public abstract int hashCode();
    // If the labelMap is null, do .equals() on nodes, else map from
    // bNode variables in one to bNodes variables in the other
    public abstract boolean equalTo(Element el2, NodeIsomorphismMap isoMap);

    @Override
    final public boolean equals(Object el2) {
        if ( this == el2 )
            return true;

        if ( !(el2 instanceof Element) )
            return false;
        return equalTo((Element)el2, null);
    }

    @Override
    public String toString() {
        return FormatterElement.asString(this);
    }

    // Constants used in hashing to stop an element and it's subelement
    // (if just one) having the same hash.

    static final int HashBasicGraphPattern    = 0xA1;
    static final int HashGroup                = 0xA2;
    static final int HashUnion                = 0xA3;
    static final int HashOptional             = 0xA4;
    // static final int HashGraph                = 0xA5; // Not needed
    static final int HashExists               = 0xA6;
    static final int HashNotExists            = 0xA7;
    static final int HashPath                 = 0xA8;
    static final int HashFetch                = 0xA9;
    static final int HashLateral              = 0xAA;
    static final int HashSemiJoin             = 0xAB;
    static final int HashAntiJoin             = 0xAC;
}
